The problem of oil and related petroleum based spills on the world's waterways is becoming an increasing problem. New and improved concepts are sought to allow for resolution of the environmental problem. One approach is the use of hydrophobic fine fibers to soak up the oil from the water surface and contain it for removal. In fact, hydrophobic fine fibers made from polypropylene were employed in the Exxon Valdez oil spill.
Various processes exist for conversion of polymeric materials, such as polypropylene, into fine fibers. The polypropylene fibers employed in the Exxon Valdez spill were made by a melt blown process. Other processes included melt spinning technology and polymer blend processes followed by extraction of one of the polymer components.
Miller and Merriam note in U.S. Pat. No. 3,097,991 that a polymer pulp can be made by extrusion of immiscible polymers followed by a paper beating type operation to separate the immiscible fibers. These fibers could then be dispersed in water to form the polymer pulp. The use of a solvent for one of the constituents of the immiscible polymer blend to liberate the fibers was noted in a similar patent by Miller and Merriam (U.S. Pat. No. 3,099,067). This patent discussed methods to make ultra-fine fibers of polyethylene, polychlorotrifluoroethylene, or polyamides. U.S. Pat. No. 3,382,305 discloses a process for the formation of oriented materials containing microfibers by blending at least two incompatible fiber-forming polymers via extrusion followed by drawing (orienting) and optionally dissolving one of the polymers from the resultant fibrous material. None of these references disclose the potential use of the fibers for oil clean-up or the utility of poly(vinyl alcohol) as a water soluble matrix for the production of the fibers.
Several Japanese patent references do mention the utility of fine fiber production using poly(vinyl alcohol) but do not extract the poly(vinyl alcohol) from the fibers. Japanese Patent Application Showa 47-67754 discloses the use of polymer mixtures incorporated into poly(vinyl alcohol) by extrusion followed by optional drawing and beating in water containing an inorganic salt to prevent poly(vinyl alcohol) solution. The resultant product was noted to be useful for paper, non-woven textiles, and can be mixed with cellulosic pulp fiberils.
Japanese Patent Application Showa 44-20869 discloses that molded articles can be formed from a water-containing poly(vinyl alcohol) and a thermoplastic polymer. This patent notes that water can be added to poly(vinyl alcohol) to render it thermoplastic. The amount of water added is 25 to 60% by weight of the poly(vinyl alcohol). Formation of fibers via poly(vinyl alcohol) extraction is not noted.
British Patent 1,206,257 discusses a blend of poly(vinyl alcohol) with polyolefins. The poly(vinyl alcohol) is plasticized to allow for thermoplastic behavior. One example (example 9) notes that fibrous webs may be produced. Again, however, extraction of the poly(vinyl alcohol) was not discussed nor was the use of these fibers for oil clean-up.
Polysulfone papers have been made by Stueben and Sommer (TAPPI, 61(1), 85 (1978) by blending polysulfone and a partially neutralized ethylene-acrylic acid copolymer followed by extrusion and cold drawing of a monofilament. Mechanical beating of the monofilament and extraction of the ethylene copolymer in a hot alkaline solution yielded polysulfone pulp which could be formed into webs using conventional paper making equipment. Various other polymer blends were discussed but did not give adequate products via this process. Poly(vinyl alcohol) was not discussed.
A unique application was proposed by Byck et. al., (Polymeric Materials for Circulatory Asst Devices; Artificial Heart Program Conference Proceedings, (R. J. Hegyeli, ed.) p. 123, U.S. Printing Office, Washington, D.C., 1969) using a blend of polypropylene and a partially neutralized ethylene-acrylic acid copolymer. The blend was extruded into a thin tape followed by orientation. When placed in a hot alkaline bath, the tape was pulled transverse to the machine direction (orientation direction) of the tape. The ethylene copolymer was extracted leaving a fine fiber web with dimensions between the fibers similar to cell dimensions. Using cell cultures from the interior of blood vessels, a cell growth could anchor on the web and present a blood compatible surface. The use of poly(vinyl alcohol) for this operation was not noted.